The present invention is generally directed to an assembly for use with a syringe and, more particularly, to a combination of a syringe and an assembly having a sealing element, an adapter and a needle shield.
Intradermal (“ID”) injections are used for delivering a variety of diagnostic and treatment compositions into a patient. ID injections are typically injections of a relatively small amount of medicament into the dermis, the dermal layer or even into a lower portion of the epidermis of a patient's skin (FIG. 1B). Substances may be injected intradermally for diagnostic testing, such as to determine a patient's immunity status against tuberculosis and the status of allergic diseases. Vaccines, drugs and other compounds may also be delivered intradermally. In many instances, ID delivery is preferred because it generally requires a smaller volume dose of the diagnostic compound or vaccine than other delivery techniques.
There is considerable variation in the thickness of a patient's skin, both between individuals and within the same individual at different sites of the body. Generally the outer skin layer, or the epidermis, typically has a thickness between two hundred and five hundred microns (200-500 μm) and the dermis, the inner and thicker layer of the skin, generally has a thickness between one and one-half to three and one-half millimeters (1.5-3.5 mm).
Administering an ID injection can be difficult and generally requires an experienced nurse or medical professional. Incorrect placement of the tip of a cannula or needle may lead to a failed injection. The placement of the cannula tip deeper than about three millimeters (3.0 mm) has the potential of delivering the injection into the subcutaneous region, where the ID dosage may be insufficient. Incorrect placement of the cannula may also puncture the skin again after being inserted into the dermis, with the delivered compound being lost on the surface of the skin. Injection is often followed by a jet effect, with the compound exiting the injection site through the puncture track. The jet effect is even more pronounced for injections through a cannula placed perpendicular to the injection site and in particular for shallow delivery.
The success of ID injections is often determined by the skill and experience of the individual healthcare professional administering the injection. A preferred ID injection technique (using a standard cannula) typically requires a healthcare professional to stretch the patient's skin, orient the cannula bevel to face upwardly, and insert a short bevel cannula at an angle of around ten to fifteen degrees)(10-15° relative to a surface of the skin, while also assuring that two to three millimeters (2-3 mm) of the cannula are located in the skin. The cannula tip ideally ends up positioned in the dermis or close to the dermis/epidermis boundary. The compound or medicament is slowly injected into the skin of the patient, forming a blister or wheal. The insertion of the cannula at an incorrect angle and/or depth results in a failed ID injection, which is typically repeated, causing additional pain and discomfort to the patient, as well as ineffective treatment to the patient. ID injection has been considered for immunization in the past, but has generally been rejected in favor of more reliable intramuscular or subcutaneous routes of administration because of the difficulty in making a successful ID injection, particularly when the injections are administered by relatively unskilled healthcare professionals.
Administration into the region of the ID space has been routinely used in the Mantoux tuberculin test, in which a purified protein derivative is injected at a shallow angle to the skin surface using a twenty-seven (27) gauge cannula and a standard syringe. The technique is known to be quite difficult to perform and generally requires specialized training. A degree of imprecision in the placement of the injection results in a significant number of false negative test results. ID injections are generally limited in volume to about 0.1 milliliter (ml), which is not enough for many common drugs. The difference with a subcutaneous injection (SQ) is only in the depo effect when a therapeutic compound is considered. ID is more effective for vaccines. Prior to injection, all needles are open and exposed either for IM, SQ or ID. ID has a shorter needle protected on one side by the adapter.
Therefore, it would be desirable to design and manufacture a syringe integral with ID adapter that allows a healthcare professional to provide a relatively simple, reliable ID injection, is relatively easy to use, is relatively cost effective to the user, limits waste of medicament, preserves a cannula closure prior to use and provides sterility of the cannula shaft and adapter sections contacting the patient skin. The devices and methods of the present invention accomplish the above objectives.